Reinforced brick masonry column with polyester thread reinforcement strips

ABSTRACT

A method of reinforcing a masonry structure is described wherein polyester thread reinforcement strips are manufactured and mounted on the masonry structure to protect it from lateral forces caused by earthquake and other natural occurring phenomena that generally produce bending moments in the masonry structure. The disclosed method can easily and economically be applied to reinforce masonry structures in underprivileged regions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 15/058,593, now allowed, filed Mar. 2, 2016, the entire contents ofeach of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to a reinforced brick masonry column withpolyester thread reinforcement strips.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

A masonry structure is generally defined as an assembly of stones,blocks and/or bricks laid one above the other using a binding materiale.g. a cement mortar. These masonry structures are adequately resistantto vertical in-plane loads, yet pose limited resistance to lateralforces caused by earthquakes, tornados, etc. due to low flexuralstrength and toughness. Several earthquakes in the recent history suchas the Great Tohoku Kanto earthquake in March 2011 in Japan, theearthquake in Chile in 2010, and the earthquake in the Northern areas ofPakistan in October 2005 were the deadliest for the people living inmasonry structures. These events left a vast trail of destruction andcrippled the economies of these countries but in spite of the dangers,people in rural areas continue to rely on masonry because it iseconomical, durable and does not require a highly skilled labor [Ashraf,M.: “Development of low-cost and efficient retrofitting technique forunreinforced masonry buildings”, Ph.D. Dissertation, University ofEngineering & Technology, Peshawar, Pakistan, (2010); Smith, A., andRedman, T.: “A critical review of retrofitting methods for unreinforcedmasonry structures”, EWB-UK Research Conference, Hosted by The RoyalAcademy of Engineering, 20 Feb. (2009); Mayorca, P. and Meguro, K.:“Proposal of an efficient technique for retrofitting unreinforcedmasonry dwellings”, Proceeding of 13th world conference on earthquakeengineering Vancouver, B.C, Canada, I: 22-29, Aug. (2004); Javed, M.:“Seismic Risk Assessment of Unreinforced Brick Masonry Systems ofNorthern Pakistan”, Ph.D. Dissertation, University of Engineering &Technology, Peshawar, Pakistan, (2009); each incorporated herein byreference in its entirety].

In the past several decades, research has been dedicated towardstrengthening and rehabilitating masonry structures. New methods haveshown to be effective against earthquakes [Ishibashi, T. and Tsukishima,D.: “Seismic damage of and seismic rehabilitation techniques for railwayreinforced concrete structures”, Journal of Advanced ConcreteTechnology, 7(3): 287-296 (2009); Cook, R. A., Doerr, G. T. andKlingner, R. E.: “Bond stress model for design of adhesive anchors”, ACIStructural Journal, 90(5): 514-24 (1993); Cook, R. A., Kunz J., Fuchs W.and Konz, R. C.: “Behavior and design of single adhesive anchors undertensile load in uncracked concrete”, ACI Structural Journal, 95(1): 9-26(1998); Zamora, N. A., Cook, R. A., Konz, R. C. and Consolazio, G. R.:“Behavior and design of single, headed and unheaded, grouted anchorsunder tensile load”, ACI Structural Journal, 100(2): 222-30 (2003);Saleem, M. and Tsubaki, T.: “Multi-layer model for pull-out behavior ofpost-installed anchor”, Proc. FRAMCOS-7, Fracture Mechanics of ConcreteStructures, AEDIFICATIO publishers, Germany, II: 823-830 (2010); Saleem,M.: “Cyclic Pull-out Push-in Shear-Lag Model for Post-Installed AnchorInfill Assembly”, Arabian Journal of Science & Technology, Volume 39,Issue 12, pp. 8537-8547, December 2014, Springer, DOI10.1007/s13369-014-1423-x; Hameed, A., Saleem, M., Qazi, A. U., Saeed,S., Ilyas, M. & Bashir, A.: “Mitigation of Seismic Pounding betweenAdjacent Buildings”, Pakistan Journal of Science, ISSN: 0030-9877, Vol.64, No. 4, Pg. 326-333, December, 2012; Hameed, A., Saleem, M., Qazi, A.U., & Rizwana, H.: “Seismic Response Evaluation of Base IsolatedBuildings”, Pakistan Journal of Science, ISSN: 0030-9877, Vol. 65, No.1, Pg. 46-54, March, 2013.; each incorporated herein by reference in itsentirety]. Many of these techniques employ post-installed anchor barsfor the retrofitting process. Among those, the most common techniquesfor increasing the confinement and performance of structures are fiberreinforced polymer wraps, post tensioning, steel jacketing, ferro-cementjacketing, concrete jacketing, and shortcreting [Ishibashi, T. andTsukishima, D.: “Seismic damage of and seismic rehabilitation techniquesfor railway reinforced concrete structures”, Journal of AdvancedConcrete Technology, 7(3): 287-296 (2009); Cook, R. A., Kunz J., FuchsW. and Konz, R. C.: “Behavior and design of single adhesive anchorsunder tensile load in uncracked concrete”, ACI Structural Journal,95(1): 9-26 (1998); Zamora, N. A., Cook, R. A., Konz, R. C. andConsolazio, G. R.: “Behavior and design of single, headed and unheaded,grouted anchors under tensile load”, ACI Structural Journal, 100(2):222-30 (2003); Saleem, M. and Tsubaki, T.: “Multi-layer model forpull-out behavior of post-installed anchor”, Proc. FRAMCOS-7, FractureMechanics of Concrete Structures, AEDIFICATIO publishers, Germany, II:823-830 (2010); Saleem, M.: “Cyclic Pull-out Push-in Shear-Lag Model forPost-Installed Anchor Infill Assembly”, Arabian Journal of Science &Technology, Volume 39, Issue 12, pp. 8537-8547, December 2014, Springer,DOI 10.1007/s13369-014-1423-x; Hameed, A., Saleem, M., Qazi, A. U.,Saeed, S., Ilyas, M. & Bashir, A.: “Mitigation of Seismic Poundingbetween Adjacent Buildings”, Pakistan Journal of Science, ISSN:0030-9877, Vol. 64, No. 4, Pg. 326-333, December, 2012; Zhuge, Y.:“FRP-Retrofitted URM Walls under in Plane Shear: Review and Assessmentof Available Models”, ASCE Journal of Composites for Construction,14(6): 743-753, (2010); Meguro, K., Mayorca, P., Sathiparan, N.,Guragain. R., and Nesheli, N.: “Shaking Table Tests of ¼ Scaled MasonryModels Retrofitted with PP-band Meshes”, Proceedings of the ThirdInternational Symposium on New Technologies for Urban Safety of MegaCities in Asia, Singapore, 1: 9-18, (2005); Coburn, A. and Spence, R.:“Earthquake Protection”, West Sussex: John Wiley & Sons Ltd., ISBN0-471-49614-6, (2002); Yoshimura, M. and Meguro, K.: “Proposal ofRetrofitting Promotion System for Low Earthquake-Resistant Structures inEarthquake Prone Countries”, Proceedings on 13th World Conference onEarthquake Engineering, Vancouver, Canada, 1(927): 221-235, (2004);Navaratnarajah, S.:” Experimental study of PP-band mesh seismicretrofitting for low earthquake masonry resisting structures: PhDDissertation, Department of Civil Engineering, University of Tokyo,Japan, (2008); Hamid, M. and Ingham, J. S.: “Diagonal CompressionTesting of FRP Retrofitted Unreinforced Clay Burnt bricks masonryWallets”, Journal of Composites for Construction, 15(5): 810-820,(2011); Turco, V., Secondin, S., Morbin, A., Valluzzi, M. R., andModena, C.: “Flexural and shear strengthening of unreinforced masonrywith FRP bars”, Composites Science and Technology, 6(1): 289-296,(2006); Sathiparan, N., Mayorca, P., Nesheli, K. N., Guragain, R. andMeguro, K.: “Experimental study on in-plain and out-of-plain behaviourof Masonry Wallettes retrofitted by PP-Band meshes”, Seisan Kenkyu, 58(3): 197-213 (2006); Bakhteri, J., Makhtar, A., and Sambasivam, S.:“Finite Element Modeling of Structural Clay Brick Masonry Subjected ToAxial Compression”, Jurnal Tecknologi, 41(B): 221-231, (2004); Farooq,S. H., Ilyas, M. and Ghaffar, A.: “Technique for strengthening ofmasonry wall panels using steel strips”, Asian Journal of CivilEngineering (Building and Housing), 7(6): 972-985, (2006); Macabuag, J.:“Dissemination of Seismic Retrofitting Techniques to Rural Communities”,EWB-UK National Research Conference, I: 13-17, (2010); each incorporatedherein by reference in its entirety]. However, these techniques usuallyrequire skilled labor, understanding of structural complexities,overcoming issues related to the lack of connectivity of theretrofitting material to the masonry [Yoshimura, M. and Meguro, K.:“Proposal of Retrofitting Promotion System for Low Earthquake-ResistantStructures in Earthquake Prone Countries”, Proceedings on 13th WorldConference on Earthquake Engineering, Vancouver, Canada, 1(927):221-235, (2004); Navaratnarajah, S.:” Experimental study of PP-band meshseismic retrofitting for low earthquake masonry resisting structures:PhD Dissertation, Department of Civil Engineering, University of Tokyo,Japan, (2008); each incorporated herein by reference in its entirety],and mostly involve large expenses to strengthen the structures. However,little attention in the past has been focused on developing a low-costpractical solution for strengthening unreinforced masonry structures inunderprivileged localities.

In view of the forgoing, one objective of the present invention is toprovide a reinforced brick masonry column, and a method for reinforcinga masonry structure by effectively mounting and tightening reinforcementstrips, which are made of a plurality of polyester threads and a matrixmaterial (e.g. an adhesive), to protect the masonry structure fromlateral forces caused by earthquakes and other natural occurringphenomena that generally produce bending moments in the masonrystructure. The disclosed method can easily and economically be appliedto reinforce masonry structures in underprivileged regions.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to areinforced brick masonry column, involving i) a brick masonry columnhaving a rectilinear cross-section comprising bricks and a mortar thatholds the bricks together at a plurality of horizontal bed joints, ii)at least one primary bonding tape wrapped around the horizontal bedjoints, iii) at least one horizontally mounted polyester threadreinforcement strip wrapped around the horizontal bed joints on top ofthe primary bonding tape, iv) at least one vertically mounted polyesterthread reinforcement strip located on each side of the brick masonrycolumn, v) at least one secondary bonding tape wrapped around thehorizontally mounted polyester thread reinforcement strips, vi) awrapping material that is wrapped horizontally around the perimeter ofthe brick masonry column, the primary bonding tape, the horizontallymounted polyester thread reinforcement strips, the vertically mountedpolyester thread reinforcement strips, the secondary bonding tape, orany combination thereof.

In one embodiment, the vertically mounted and the horizontally mountedpolyester thread reinforcement strips comprise a plurality of paralleland adjacent polyester threads and an adhesive that holds the polyesterthreads together with no gap therebetween.

In one embodiment, the adhesive is at least one selected from the groupconsisting of an epoxy, a urethane, a polyimide, an acrylate, apolyvinyl acetate, and a polyethylene-vinyl acetate.

In one embodiment, the vertically mounted polyester thread reinforcementstrips interweave through the horizontally mounted polyester threadreinforcement strips.

In one embodiment, the width and the thickness of the vertically mountedpolyester thread reinforcement strips are substantially similar to thewidth and the thickness of the horizontally mounted polyester threadreinforcement strips.

In one embodiment, the thickness of the vertically mounted polyesterthread reinforcement strips is at least 5% greater than the thickness ofthe horizontally mounted polyester thread reinforcement strips.

In one embodiment, the width of the vertically mounted polyester threadreinforcement strips is at least 5% greater than the width of thehorizontally mounted polyester thread reinforcement strips.

In one embodiment, the width of the horizontally mounted polyesterthread reinforcement strips is in the range of 10-30 mm relative to thehorizontal bed joints having a width in the range of 5-15 mm, andwherein the horizontally mounted polyester thread reinforcement stripsentirely cover the horizontal bed joints.

In one embodiment, the width of the horizontally mounted polyesterthread reinforcement strips is in the range of 10-30 mm relative to thebrick masonry column having a height in the range of 1-10 m.

In one embodiment, the wrapping material covers at least half of theheight of the reinforced brick masonry column.

In one embodiment, the reinforced brick masonry column has at least oneof the following properties, i) a failure peak ground acceleration atleast 9% higher than a failure peak ground acceleration in the brickmasonry column, ii) a strain energy before failure at least 5% higherthan a strain energy before failure in the brick masonry column, iii) apost-failure displacement at the top of the reinforced brick masonrycolumn at least 20% lower than a post-failure displacement at the top ofthe brick masonry column, or iv) a post-failure crack width that isnarrower than a post-failure crack width in the brick masonry column.

According to a second aspect, the present disclosure relates to a methodof strengthening a brick masonry column comprising bricks and a mortarthat holds the bricks together at a plurality of horizontal bed joints,the method involving i) wrapping each horizontal bed joint in the brickmasonry column with at least one layer of a primary bonding tape, ii)wrapping a polyester thread reinforcement strip on the primary bondingtape at each horizontal bed joint to form horizontally mounted polyesterthread reinforcement strips, iii) vertically mounting at least onepolyester thread reinforcement strip on each side of the brick masonrycolumn by interweaving through the horizontally mounted polyester threadreinforcement strips to form a meshed structure that is wrapped aroundthe brick masonry column, iv) wrapping the horizontally mountedpolyester thread reinforcement strips with at least one layer of asecondary bonding tape, v) covering at least a portion of the brickmasonry column, the primary bonding tape, the meshed structure, thesecondary bonding tape, or combinations thereof with at least one layerof a wrapping material.

In one embodiment, a first horizontal bed joint from the bottom of thebrick masonry column is wrapped with at least one layer of the primarybonding tape and at least two layers of the horizontally mountedpolyester thread reinforcement strips.

In one embodiment, at least two polyester thread reinforcement stripsare vertically mounted on each side of the brick masonry column and thetwo polyester thread reinforcement strips are separated by a distance ofat least 2 cm.

In one embodiment, the meshed structure has a rectangular shape in thesize range of 2-30 cm by 2-30 cm.

In one embodiment, the width of the horizontally mounted polyesterthread reinforcement strips is in the range of 10-30 mm relative to thehorizontal bed joints having a width in the range of 5-15 mm, whereinthe horizontally mounted polyester thread reinforcement strips entirelycover the horizontal bed joints.

In one embodiment, the width of the horizontally mounted polyesterthread reinforcement strips is in the range of 10-30 mm relative to thebrick masonry column having a height in the range of 1-10 m.

According to a third aspect, the present disclosure relates to a methodof manufacturing polyester thread reinforcement strips, involving i)tying a first end of a polyester thread to a first pole of a structurecomprising the first pole and a second pole, wherein the first pole andthe second pole are parallel and separated by at least 20 cm, ii)winding a second end of the polyester thread around the second pole ofthe structure and returning the second end of the polyester thread tothe first pole in stretched form to make a wound cycle, wherein thepolyester thread is perpendicular to the first and second poles, iii)repeating the winding at least 30 times in a back and forth movement toform a polyester thread assembly, wherein each polyester thread isadjacent and parallel to the polyester thread from a previous woundcycle, and wherein no gap is present between the adjacent and parallelpolyester threads, iv) applying an adhesive to the polyester threadassembly, v) curing and/or drying the adhesive, vi) cutting thepolyester thread assembly along the first and second poles and at least1 cm from each pole to make the polyester thread reinforcement strip.

In one embodiment, the cutting forms cut edges on opposing sides of thepolyester thread reinforcement strip, and the method further comprisessealing the cut edges of the polyester thread reinforcement strip byheating, annealing and/or taping.

In one embodiment, the polyester thread reinforcement strip has anultimate tensile strength at least four times larger and a maximumtensile load bearing capacity at least three times larger than asubstantially similar strip with polypropylene threads instead ofpolyester threads.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A is a representation of a brick masonry column.

FIG. 1B is a magnified representation of a horizontal bed joint, whereintwo adjoining bricks are bonded together by a mortar.

FIG. 2A is a representation of a reinforced brick masonry column withpolyester thread reinforcement strips wrapped around the reinforcedbrick masonry column.

FIG. 2B is a representation of interwoven polyester thread reinforcementstrips mounted on the reinforced brick masonry column.

FIG. 3 represents an experimental setup of a masonry column on a shaketable.

FIG. 4 shows a cement concrete platform which is used as a support padfor the brick masonry column.

FIG. 5 shows a polyester thread reinforcement strip.

FIG. 6 shows the East-West component of the acceleration time-history ofEl-Centro earthquake.

FIG. 7 represents an overlay of drive ground acceleration applied to abrick masonry column, and the resulting feedback ground acceleration.

FIG. 8 shows the feedback ground acceleration of the brick masonrycolumn and the reinforced brick masonry column.

FIG. 9 shows the top and bottom displacement of the brick masonry columnat a peak ground acceleration of 2.40 m/s².

FIG. 10 shows the top and bottom displacement of the reinforced brickmasonry column at a peak ground acceleration of 2.60 m/s².

FIG. 11A shows the displacement response in the reinforced brick masonrycolumn prior to failure.

FIG. 11B shows the change of mode in displacement response in thereinforced brick masonry column prior to failure.

FIG. 12 shows an overlay of the top displacement of the brick masonrycolumn and the reinforced brick masonry column at a peak groundacceleration of 2.40 m/s².

FIG. 13A shows the maximum displacements at the top in the brick masonrycolumn.

FIG. 13B shows the maximum displacements at the top in the reinforcedbrick masonry column.

FIG. 14A shows the crack pattern after failure in the first bed joint ofthe brick masonry column.

FIG. 14B shows the crack pattern after failure in the second bed jointof the brick masonry column.

FIG. 15A shows the first, the second, and the third cracks in thereinforced brick masonry column after failure.

FIG. 15B shows the second and the third cracks in the reinforced brickmasonry column after failure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

According to a first aspect, the present disclosure relates to areinforced brick masonry column 201, involving a brick masonry column101 having a rectilinear cross-section comprising bricks 102 and amortar 103 that bonds the bricks 102 together at a plurality ofhorizontal bed joints 104.

Horizontal bed joints as used herein, refers to bed joints that form anangle in the range of 0-30 degrees, preferably 0-10 degrees, morepreferably 0-5 degrees with horizon.

Masonry column as used herein refers to a structure that is constructedfrom building blocks laid in and bound together by a mortar 103. Thebuilding blocks may be brick, marble, granite, travertine, limestone,cast stone, concrete block, glass block, and/or cob, although, brick andconcrete blocks are the most common types of building blocks. Masonrycolumns are durable forms of construction. Durability of a masonrycolumn may vary significantly depending on the type of the buildingblocks, the quality of mortar, and the pattern in which the buildingblocks are assembled. Masonry columns are resistant to projectiles, e.g.debris from hurricanes or tornadoes. Masonry columns have highcompressive strength under vertical loads, but they show a very limitedstrength when bending, stretching, or twisting.

Mortar as used herein refers to a paste-like adhesive used to bind thebuilding blocks together at bed joints, wherein adjacent surfaces ofadjoining bricks meet. The mortar comprises at least a portion of abinder (e.g. cement), a portion of water, and a portion of an aggregate(e.g. sand).

In one or more embodiments, Portland cement may be used to bind the sandaggregate, wherein the weight ratio of cement to sand may be in therange of 0.05-0.6, preferably 0.15-0.4, and more preferably 0.25.

In one embodiment, the mortar 103 may be cured for duration in the rangeof 2-200 hours, preferably 150-200 hours, and more preferably 170 hours.

In one embodiment, bonding of the brick masonry column 101 is at leastone selected from the group consisting of Flemish bond, Monk bond,Sussex bond, English bond, English cross bond, Scottish bond, Americanbond, Stretcher bond, and Header bond.

In one embodiment, the bricks 102 may have rectangular cross-section,wherein the length is in the range of 10-50 cm, preferably 15-40 cm, andmore preferably 23 cm. The bricks 102 may have a width in the range of3-30 cm, preferably 5-15 cm, and more preferably 11 cm. The bricks 102may have a thickness in the range of 2-20 cm, preferably 3-12 cm, andmore preferably 8 cm. Although these dimension ranges for the bricks arepreferred, they are not limiting the brick sizes, and brick dimensionsoutside of these ranges may also be used. In one embodiment, the bricks102 may have a polygonal cross-section e.g. triangular, pentagonal(5-sided), and/or hexagonal (6-sided).

In one embodiment, the brick masonry column 101 has a rectangularcross-section, wherein the length is in the range of 0.05-10 m,preferably 0.1-1 m, more preferably 0.25 m relative to the width of thebrick masonry column 101 in the range of 0.05-0.5 m, preferably 0.2-0.3m, more preferably 0.25 m. In one embodiment, the height of the brickmasonry column 101 may be in the range of 1-10 m, preferably 1-5 m, morepreferably 1.5-3 m.

In one embodiment, the width of the horizontal bed joints 104 may be inthe range of 5-80 mm, preferably 5-30 mm, more preferably 5-15 mm,relative to the height of the brick masonry column 101 in the range of1-10 m, preferably 1-5 m, more preferably 1.5-3 m.

The reinforced brick masonry column 201, further includes primarybonding tape 202 wrapped around the horizontal bed joints 104.

The primary bonding tape as used herein may refer to any tape that has alength and a width and has an adhesive layer on at least one side of thetape. In one embodiment, the primary bonding tape 202 may be asingle-sided tape (i.e. a layer of an adhesive on one side of the tape),or a double-sided tape (i.e. two layers of an adhesive on both sides ofthe tape). In one embodiment, the tape in the primary bonding tape 202may be made of plastic (e.g. vinyl or latex), or fabric (e.g. cotton orpolyester), and the adhesive layer may be alkyl-acrylates and/orrubber-based adhesives. In one embodiment, the primary bonding tape 202may be duct tape, bondage tape, electrical tape, scotch tape, GorillaTape®, and/or surgical tape, etc.

In one embodiment, at least one layer of the primary bonding tape 202may be wrapped around one or more horizontal bed joints 104.

In one embodiment, the width of the horizontal bed joints 104 is in therange of 5-80 mm, preferably 5-30 mm, and more preferably 5-15 mm, andthe primary bonding tape 202 has a width in the range of 10-100 mm,preferably 10-60 mm, more preferably 10-40 mm, and the primary bondingtape 202 may entirely cover the horizontal bed joints 104. In oneembodiment, the primary bonding tape 202 may cover at least a portion ofthe adjoining bricks.

The reinforced brick masonry column 201, further involves horizontallymounted polyester thread reinforcement strips 204 wrapped around thehorizontal bed joints 104 on top of the primary bonding tape 202.

The horizontally mounted polyester thread reinforcement strips as usedherein comprise a plurality of parallel and adjacent polyester threadsand a matrix material (e.g. an adhesive) that holds the polyesterthreads together with no gap therebetween (additional description ofpolyester thread reinforcement strips is provided in the third aspect ofthis disclosure).

In one embodiment, the horizontally mounted polyester threadreinforcement strips 204 are mounted and secured horizontally over theprimary bonding tape 202 to confine and protect the horizontal bedjoints 104.

In one embodiment, the width of the horizontally mounted polyesterthread reinforcement strips 204 may be in the range of 10-30 mm relativeto the horizontal bed joints 104 having a width in the range of 5-80 mm,preferably 5-30 mm, and more preferably 5-15 mm, wherein thehorizontally mounted polyester thread reinforcement strips 204 mayentirely cover the horizontal bed joints 104.

In one embodiment, the width of the horizontally mounted polyesterthread reinforcement strips 204 is in the range of 10-80 mm, preferably10-40 mm, or around 20 mm relative to the brick masonry column 101having a height in the range of 1-10 m, preferably 1-5 m, morepreferably 1.5-3 m. In one embodiment, the thickness of the horizontallymounted polyester thread reinforcement strips 204 is in the range of0.5-10 mm, preferably 1-5 mm, and more preferably 1.5-2 mm.

In one embodiment, at least one layer of the horizontally mountedpolyester thread reinforcement strips 204 are wrapped around thehorizontal bed joints 104.

The width of the primary bonding tape may be equal to or greater thanthe width of the horizontally mounted polyester thread reinforcementstrips. In one embodiment, the width of the primary bonding tape 202 islarger than the width of the horizontally mounted polyester threadreinforcement strips 204.

In one embodiment, a first horizontal bed joint from the bottom of thebrick masonry column 101 may be wrapped with at least two layers of theprimary bonding tape 202 and at least two layers of the polyester threadreinforcement strips, wherein one of the polyester thread reinforcementstrips may be located between the at least two layer of the primarybonding tape 202 to increase joint performance at the first horizontalbed joint.

The reinforced brick masonry column 201, further involves verticallymounted polyester thread reinforcement strips 203 located on each sideof the brick masonry column 101.

The vertically mounted polyester thread reinforcement strips as usedherein comprise a plurality of parallel and adjacent polyester threadsand a matrix material (e.g. an adhesive) that holds the polyesterthreads together with no gap therebetween (additional description ofpolyester thread reinforcement strips is provided in the third aspect ofthis disclosure).

In one embodiment, at least two vertically mounted polyester threadreinforcement strips 203 may be mounted on each side of the brickmasonry column 101, and they may be separated by a distance in the rangeof 2-30 cm, preferably 5-15 cm, and more preferably 10 cm.

In one embodiment, the vertically mounted polyester thread reinforcementstrips 203 are mounted vertically along the height of the brick masonrycolumn 101. In one embodiment, the vertically mounted polyester threadreinforcement strips 203 cover at least 50%, or at least 60%, or atleast 70%, or at least 80% of the height of the brick masonry column101, wherein the vertically mounted polyester thread reinforcementstrips 203 are mounted on a lower portion of the brick masonry column101. In one embodiment, the vertically mounted polyester threadreinforcement strips 203 cover at least 50%, or at least 60%, or atleast 70%, or at least 80% of the height of the brick masonry column101, wherein the vertically mounted polyester thread reinforcementstrips 203 are mounted on an upper portion of the brick masonry column101.

In one embodiment, the vertically mounted polyester thread reinforcementstrips 203 interweave through the horizontally mounted polyester threadreinforcement strips 204 to form a meshed structure that confines thebrick masonry column 101.

In one embodiment, meshes in the meshed structure may have a rectangularshape in the size range of 2-30 cm by 2-30 cm, preferably 5-15 cm by5-15 cm.

In one embodiment, the width and the thickness of the vertically mountedpolyester thread reinforcement strips 203 are substantially similar tothe width and the thickness of the horizontally mounted polyester threadreinforcement strips 204.

In one embodiment, the vertically mounted polyester thread reinforcementstrips 203 have a thickness at least 5%, or at least 6%, or at least 7%,or at least 8%, or at least 9%, or at least 10%, or at least 15%, or atleast 20% greater than the thickness of the horizontally mountedpolyester thread reinforcement strips 204. In one embodiment, thethickness of the vertically mounted polyester thread reinforcementstrips 203 is in the range of 0.5-10 mm, preferably 1-5 mm, and morepreferably 2-3 mm.

In one embodiment, the width of the vertically mounted polyester threadreinforcement strips 203 may be at least 5%, or at least 6%, or at least7%, or at least 8%, or at least 9%, or at least 10%, or at least 15%, orat least 20% greater than the width of the horizontally mountedpolyester thread reinforcement strips 204. In one embodiment, the widthof the vertically mounted polyester thread reinforcement strips 203 isin the range of 10-80 mm, preferably 20-50 mm, or around 30 mm.

The reinforced brick masonry column 201, further includes secondarybonding tape wrapped around the horizontally mounted polyester threadreinforcement strips 204.

The secondary bonding tape as used herein may refer to any tape that hasa length and a width and has an adhesive layer on at least one side ofthe tape. In one embodiment, the secondary bonding tape may be asingle-sided tape (i.e. a layer of an adhesive on one side of the tape),or a double-sided tape (i.e. two layers of an adhesive on both sides ofthe tape). In one embodiment, the tape in the secondary bonding tape maybe made of plastic (e.g. vinyl or latex), or fabric (e.g. cotton orpolyester), and the adhesive layer may be alkyl-acrylates and/orrubber-based adhesives. In one embodiment, the secondary bonding tape202 may be duct tape, bondage tape, electrical tape, scotch tape,Gorilla Tape®, and/or surgical tape, etc.

In one embodiment, the primary bonding tape 202 and the secondarybonding tape are substantially similar in terms of dimensions, single ordouble sidedness, material, or any combination thereof.

In one embodiment, at least one layer of the secondary bonding tape iswrapped around the horizontal bed joints 104.

In one embodiment, the width of the horizontal bed joints 104 are in therange of 5-80 mm, preferably 5-30 mm, and more preferably 5-15 mm, andthe secondary bonding tape has a width in the range of 10-100 mm,preferably 10-60 mm, more preferably 10-50 mm, and the secondary bondingtape entirely covers the horizontal bed joints 104, the primary bondingtape 202, and the horizontally mounted polyester thread reinforcementstrips 204. In one embodiment, the secondary bonding tape only covers atleast a portion of the adjoining bricks.

The reinforced brick masonry column 201, further involves a wrappingmaterial 205 that is wrapped horizontally around the perimeter of thebrick masonry column 101, the primary bonding tape 202, the horizontallymounted polyester thread reinforcement strips 204, the verticallymounted polyester thread reinforcement strips 203, the secondary bondingtape, or any combination thereof.

In one embodiment, the wrapping material 205 covers at least 50% of theheight of the brick masonry column 101, wherein the wrapping material205 covers the upper half of the brick masonry column 101. In oneembodiment, the wrapping material 205 covers at least 50% of the heightof the brick masonry column 101, wherein the wrapping material 205covers the lower half of the brick masonry column 101.

In one embodiment, the wrapping material 205 is made of rubber, nylon,polypropylene, polyvinyl chloride (PVC), low density polyethylene(LDPE), fabric, and/or cardboard.

In one embodiment, the wrapping material 205 has a width in the range of1-30 cm, preferably 5-10 cm, relative to the height of the brick masonrycolumn 101 which is in the range of 1-10 m, preferably 1-5 m, morepreferably 1.5-3 m.

In one embodiment, the wrapping material 205 has a thickness in therange of 0.1-10 mm, preferably 1-5 mm, relative to the height of thebrick masonry column 101 which is in the range of 1-10 m, preferably 1-5m, more preferably 1.5-3 m.

In one embodiment, a base 401 of the brick masonry column 101 or thereinforced brick masonry column 201 is secured in a cement concrete pad402, wherein at least 20%, preferably at least 40%, but no more than 50%of the thickness of the brick 102, which is located at the base 401, isinserted into the cement concrete pad 402, as shown in FIG. 4.

In one embodiment, the brick masonry column 101 and the reinforced brickmasonry column 201 are attached to a shake table 301 and transducers 302to measure dynamic properties such as peak ground acceleration (PGA),strain energy before failure, and post-failure displacement.

A shake table as used herein may refer to a device for shaking astructure or a building with a range of simulated ground motions. Testspecimen is fixed on platform of the shake table 301, and it is shakento the point of failure. Under an applied ground motion, dynamicproperties of the test specimen such as peak ground acceleration (PGA),strain energy before failure, and post-failure displacement can bereadily measured using video records and/or data from the transducers302.

Peak ground acceleration (PGA) as used herein refers to a ground shakingthat is equal to a maximum ground acceleration that occurs duringearthquake shaking. Failure peak ground acceleration is equal to theamplitude of the largest acceleration recorded on the transducers 302.Shake tables may be used to investigate the response of a structure toground accelerations and to evaluate seismic performance of thestructure.

Strain energy before failure as used herein refers to the amount ofenergy that a structure can absorb without failure in bending/flexuralmode. Strain energy before failure for a structure may be measured byintegrating a representative force-displacement curve, or arepresentative stress-strain curve up to a point of failure. Strainenergy is the amount of energy absorbed by the structure to bend.

The post-failure displacement at the top of a column as used herein maybe a measure of sway at the top of the column after failure (i.e. thepost-failure displacement is an indication of column stability afterfailure by showing how much a failed column move backward and forward,or side to side).

In one embodiment, the reinforced brick masonry column 201 has a failurepeak ground acceleration at least 9% higher than a failure peak groundacceleration in the brick masonry column 101. In one embodiment, thefailure peak ground acceleration in the reinforced brick masonry column201 is in the range of 2.4-3.0 m/s², preferably 2.5-2.65 m/s², and morepreferably 2.6 m/s². In one embodiment, the failure peak groundacceleration in the brick masonry column 101 is in the range of 2.0-2.6m/s², preferably 2.3-2.5 m/s², and more preferably 2.4 m/s².

In one embodiment, the strain energy before failure in the reinforcedbrick masonry column 201 is 15% higher, preferably 10% higher, and morepreferably 5% higher than the strain energy before failure in the brickmasonry column 101.

In one embodiment, upon failure the reinforced brick masonry column 201has a post-failure crack width that is narrower than the post-failurecrack width in the brick masonry column 101. In one embodiment, uponfailure a wide post-failure crack may be formed at the bottom of thebrick masonry column 101, wherein a narrow post-failure crack may beformed along the height of the reinforced brick masonry column 201,implying that the strain energy may be uniformly distributed along thereinforced brick masonry column 201, as oppose to the brick masonrycolumn 101 wherein strain energy may be non-uniformly distributed.

The post-failure crack as used herein may refer to a crack that formsupon failure in the brick masonry column 101, and has the largest width.Width of the crack may be measured with a measuring tape, a laser, acamera and/or a digital image correlation (DIC) system.

In one embodiment, at ground acceleration equal to the failure peakground acceleration of the brick masonry column 101, the post-failuredisplacement at the top of the brick masonry column 101 is in the rangeof 5-20 cm, preferably 5-10 cm, more preferably around 8.6 cm, as shownin FIG. 13A. In one embodiment, at a ground acceleration equal to thefailure peak ground acceleration of the reinforced brick masonry column201, the post-failure displacement at the top of the reinforced brickmasonry column 201 is in the range of 5-15 cm, preferably 5-8 cm, morepreferably around 6.8 cm, as shown in FIG. 13B. In one embodiment, thepost-failure displacement at the top of the reinforced brick masonrycolumn 201 is at least 30%, preferably 25%, and more preferably 21%lower than the post-failure displacement at the top of the brick masonrycolumn 101.

According to a second aspect, the present disclosure relates to a methodof strengthening the brick masonry column 101, involving wrapping thehorizontal bed joints 104 in the brick masonry column 101 with at leastone layer of the primary bonding tape 202.

In one embodiment, the primary bonding tape 202 may be cut into shortprimary bonding tape, wherein the width and the thickness of the shortprimary bonding tape are substantially similar to the primary bondingtape 202 before being cut. In one embodiment, the short primary bondingtape may be secured perpendicular to each other on the horizontal bedjoints 104, wherein a first short primary bonding tape is secured on ahorizontal bed joint (i.e. is secured in a horizontal fashion) and atleast a second short primary bonding tape is secured perpendicular tothe first short primary bonding tape (i.e. is secured in a verticalfashion). In one embodiment, the second short primary bonding tape issecured on the horizontal bed joints 104, such that the angle betweenthe first and the second short primary bonding tapes is in the range of5-175 degrees, preferably 30-150 degrees, more preferably 45-135degrees.

The method of strengthening further involves wrapping the polyesterthread reinforcement strip on the primary bonding tape 202 at thehorizontal bed joints 104 to form horizontally mounted polyester threadreinforcement strips 204. In one embodiment, a plurality of thepolyester thread reinforcement strips may be wrapped around a horizontalbed joint.

In one embodiment, the polyester thread reinforcement strips may be cutinto short strips, wherein the width and the thickness of the shortstrips are substantially similar to the polyester thread reinforcementstrips prior to being cut. In one embodiment, a plurality of the shortstrips may be mounted on the horizontal bed joints 104 to cover at leasta portion of the length of the horizontal bed joints 104. In oneembodiment, the short strips are mounted parallel to each other on thehorizontal bed joints 104. In one embodiment, a first short strip ismounted on a horizontal bed joint and at least a second short strip ismounted on the first short strip and the horizontal bed joints 104, suchthat the angle between the first and the second short strips is in therange of 10-170 degrees, preferably 30-150 degrees, more preferably45-135 degrees.

The method of strengthening further involves vertically mounting thepolyester thread reinforcement strips on each side of the brick masonrycolumn 101 to form vertically mounted polyester thread reinforcementstrips 203.

In one embodiment, at least one layer of the vertically mountedpolyester thread reinforcement strip interweave through the horizontallymounted polyester thread reinforcement strips 204 to form the meshedstructure that confines the brick masonry column 101.

In one embodiment, the vertically mounted polyester thread reinforcementstrips 203 and the horizontally mounted polyester thread reinforcementstrips 204 may be glued or otherwise secured together at intersections,wherein the horizontally mounted polyester thread reinforcement strips204 and the vertically mounted polyester thread reinforcement strips 203intersect.

The method of strengthening a brick masonry column 101 further involveswrapping the horizontally mounted polyester thread reinforcement strips204 with at least one layer of a secondary bonding tape.

In one embodiment, the secondary bonding tape may be cut into shortsecondary bonding tape, wherein the width and the thickness of the shortsecondary bonding tape are substantially similar to the secondarybonding tape prior to being cut. In one embodiment, the short secondarybonding tapes may be secured perpendicular to each other on thehorizontal bed joints 104, wherein a first short secondary bonding tapeis secured on a horizontal bed joint and at least a second shortsecondary bonding tape is secured perpendicular to the first shortsecondary bonding tape. In one embodiment, the second short secondarybonding tape is secured on the horizontal bed joints 104, such that theangle between the first and the second short secondary bonding tapes isin the range of 5-175 degrees, preferably 30-150 degrees, morepreferably 45-135 degrees.

The method of strengthening a brick masonry column 101 further involvescovering at least a portion of the brick masonry column 101, the primarybonding tape 202, the meshed structure, the secondary bonding tape, orcombinations thereof with at least one layer of a wrapping material 205.

In one embodiment, a string, a wire, a cord, a cable with a diameter ina range of 1-20 mm, preferably 1-10 mm, more preferably 1-5 mm, and/or aplastic/cotton rope with a diameter in a range of 1-20 mm, preferably1-10 mm, more preferably 1-5 mm, may be used to hold the wrappingmaterial 205 around the perimeter of the brick masonry column 101.

In addition to brick masonry columns having rectilinear cross-sections,brick masonry columns having other shaped cross-sections can beenvisioned. For example, the brick masonry column may have a circularcross-section (i.e. a cylindrical column), wherein the height is in therange of 1-10 m, preferably 1-5 m, more preferably around 3 m, relativeto the diameter which is in the range of 0.2-2 m, preferably 0.5-1 m.

In one embodiment, the brick masonry column has a circular cross-section(i.e. a cylindrical column), wherein the method of strengthening issubstantially similar to the method of strengthening in the brickmasonry column 101 having a rectilinear cross-section.

In one embodiment, the brick masonry column has a circular cross-sectionand the polyester thread reinforcement strips are circumferentiallymounted around the perimeter of the brick masonry column. In oneembodiment, the brick masonry column has a circular cross-section andthe polyester thread reinforcement strips are coiled around theperimeter of the brick masonry column.

According to a third aspect, the present disclosure relates to a methodof manufacturing polyester thread reinforcement strips 500 using apolyester thread 501, as shown in FIG. 5. The method involves, tying afirst end of the polyester thread 501 to a first pole of a structurecomprising the first pole and a second pole, wherein the first pole andthe second pole are substantially similar and parallel to each other,and are separated by a distance in the range of 10-200 cm, preferably20-100 cm, more preferably around 50 cm.

Polyester threads as used herein may be made by melting a polyesterpolymer (e.g. polyethylene terephthalate) at a temperature in the rangeof 200-300° C., preferably 230-300° C., more preferably about 260° C. toform a molten polymer. The molten polymer is then extruded through aspinneret and quenched to form the polyester threads. The polyesterthreads are wound on large bobbins or flat-wound packages. In oneembodiment, the molten polymer is extruded through a die with a circularcross-section and quenched to form the polyester threads. In oneembodiment, the die has a rectilinear cross-section.

In one embodiment, polyester threads comprise a plurality of intertwinedseparate polyester fibrils. Each polyester fibril may have a circularcross-section with the diameter in the range of 10-100 μm, preferably20-80 μm, preferably 30-70 μm, preferably about 50 μm. In oneembodiment, the plurality of intertwined separate polyester fibrils arecoated with polyethylene to form the polyester threads.

In one embodiment, the polyester threads have a circular cross-sectionwith the diameter in the range of 0.1-2 mm, preferably 0.5-1 mm.

In one embodiment, the polyester threads include at least one polymerselected from the group consisting of polyglycolide, polylactic acid,polycaprolactone, polyhydroxyalkanoate, polyhydroxybutyrate,polyethylene adipate, polybutylene succinate, polyethyleneterephthalate, polybutylene terephthalate, polytrimethyleneterephthalate, polyethylene naphthalate, and vectran.

In one embodiment, polyester threads are at least 5%, or at least 10%,or at least 15%, or at least 20%, or at least 30%, or at least 40%, orat least 50%, or at least 60%, or at least 100% more UV resistant thanpolypropylene threads.

In one embodiment, polyester threads have a tensile strength of at least5%, or at least 10%, or at least 15%, or at least 20%, or at least 30%,or at least 40%, or at least 50%, or at least 60%, or at least 100%larger than the tensile strength of polypropylene threads.

In one embodiment, polyester threads have a creep resistance of at least5%, or at least 10%, or at least 15%, or at least 20%, or at least 30%,or at least 40%, or at least 50%, or at least 60%, or at least 100%higher than the creep resistance of polypropylene threads.

In one embodiment, melting point of polyester threads is in the range of200-300° C., preferably 230-300° C., more preferably about 260° C. Inone embodiment, melting point of polypropylene threads is in the rangeof 100-200° C., preferably 100-160° C., more preferably about 130° C.

In one embodiment, polyester threads are at least 5%, or at least 10%,or at least 15%, or at least 20%, or at least 30%, or at least 40%, orat least 50%, or at least 60%, or at least 100% more resistant to agingand abrasion than polypropylene threads.

The method of manufacturing further involves winding a second end (i.e.free end) of the polyester thread around the second pole of thestructure and returning the second end of the polyester thread to thefirst pole in stretched form to make a wound cycle, wherein thepolyester thread is perpendicular to the first and second poles.

The method of manufacturing further involves repeating the winding atleast 20 times in a back and forth movement to form a polyester threadassembly, wherein each polyester thread is adjacent and parallel to thepolyester thread from a previous wound cycle, and wherein no gap ispresent between the adjacent and parallel polyester threads.

No gap as used herein may refer to an embodiment wherein polyesterthreads are in proximity of each other but not directly adjacent, and amatrix material (i.e. an adhesive) is present between the polyesterthreads.

The method of manufacturing further involves applying an adhesive to thepolyester thread assembly.

In one embodiment, the adhesive may be selected from the groupconsisting of epoxy, urethane, polyimides, acrylates, polyvinyl acetate,and polyethylene-vinyl acetate.

The method of manufacturing further involves curing and/or drying theadhesive.

Depending on the type of adhesive used, curing and/or drying may beadopted. For example, a solvent based adhesive (e.g. acrylates, orpolyvinyl acetate) may require drying. Drying as used herein may referto an action that removes solvent from the adhesive. Depending on thetype of solvent, heating, room-temperature drying, and/or vacuum dryingmay be used. The adhesives such as epoxy, urethane, polyimides, etc. mayrequire curing to solidify. Curing as used herein may refer to anyaction that initiates a crosslinking reaction and increases themolecular weight of the adhesive. Curing may be performed by applyingheat, and/or UV irradiation to the adhesive.

The method of manufacturing further involves cutting the polyesterthread assembly along the first and the second poles and at least 1 cm,or at least 2 cm, or at least 5 cm, or at least 10 cm, from each pole tomake the polyester thread reinforcement strip.

In one embodiment, cutting the polyester thread assembly along the firstand the second poles forms cut edges on opposing sides of the polyesterthread reinforcement strip, and the method further comprises sealing thecut edges of the polyester thread reinforcement strip by heating,annealing and/or taping.

In one embodiment, the polyester thread reinforcement strips may have awidth in the range of 10-80 mm, preferably 10-50 mm, relative to thethickness which is in the range of 0.5-10 mm, preferably 1-5 mm, morepreferably 1-3 mm. In one embodiment, the length of the polyester threadreinforcement strips may be in the range of 5-200 cm, preferably 20-100cm, more preferably around 50 cm.

Standard procedure for measuring tensile properties of plastics (ASTMD638) is conducted through the use of a universal testing machine tocharacterize the tensile properties of the polyester threadreinforcement strips. In one embodiment, the polyester threadreinforcement strip has an ultimate tensile strength at least four timeslarger and a maximum tensile load bearing capacity at least three timeslarger than a substantially similar strip with polypropylene threadsinstead of polyester threads.

Ultimate tensile strength as used herein may refer to a maximum stressin tensile mode that the polyester thread reinforcement strip can endurewithout failure. Additionally, load bearing capacity as used herein mayrefer to a maximum load in tensile mode that the polyester threadreinforcement strip can endure without failure. Since ultimate tensilestrength is a geometry-independent property (i.e. independent ofdimensions of the polyester thread reinforcement strip), it may be thepreferred quantity over the load bearing capacity, which is ageometry-dependent property (i.e. depends on dimensions of the polyesterthread reinforcement strip).

In one embodiment, the method of manufacturing further comprises apolyester fabric, a polyester blend fabric, and/or a cotton fabricinstead of the polyester thread assembly, to produce a fabricreinforcement strip. In one embodiment, the adhesive may be applied to astack of polyester fabrics to produce the fabric reinforcement strip. Inone embodiment, the stack of polyester fabrics comprises at least aplurality of polyester fabrics. In one embodiment, the stack ofpolyester fabrics comprises a first polyester fabric and a secondpolyester fabric, wherein the angle between polyester threads in thefirst polyester fabric and polyester threads in the second polyesterfabric may be in the range of 0-180 degrees, preferably 30-150 degrees,more preferably 45-135 degrees.

In one embodiment, manufacturing cost for the reinforced brick masonrycolumn using the method of strengthening is at least 80%, or at least90%, or at least 100%, or at least 120% less expensive than steel-jacketstrengthening method. In one embodiment, manufacturing cost for thereinforced brick masonry column using the method of strengthening is atleast 150%, or at least 180%, or at least 200%, or at least 220% lessexpensive than concrete-jacket strengthening method. In one embodiment,manufacturing cost for the reinforced brick masonry column using themethod of strengthening is at least 1500%, or at least 2000%, or atleast 2500%, or at least 2800% less expensive than FRP-jacket (FiberReinforced Polymer) strengthening method. In one embodiment, the methodof strengthening does not require skilled labor, as oppose tosteel-jacket, concrete-jacket, or FRP-jacket strengthening methods,wherein skilled labor is required.

The examples below are intended to further illustrate protocols fordesigning and manufacturing the reinforced brick masonry column 201 andthe polyester thread reinforcement strip, as well as characterizing andcomparing seismic and mechanical performances and are not intended tolimit the scope of the claims.

Example 1

A brick masonry column, as shown in FIG. 1A, was used as the testspecimen in the present study. The test specimen had a squarecross-section of 9 inch×9 inch (0.23 m×0.23 m) and 6 ft (1.83 m) height.Three identical test specimens were tested; an unstrengthened column(i.e. unreinforced or control), and two strengthened columns (i.e.reinforced) with certain configuration of polyester strips. In thestrengthened columns, each polyester strip was mounted at the joint ofbricks and wrapped using a bonding tape, followed by a global wrappingfrom the bottom of the column as shown in FIG. 2A. Shake test wasconducted on a uniaxial shaking table as shown in FIG. 3. Bottom ends ofall the specimens were fixed to the shaking table whereas the top endwas free to sway as shown in FIG. 3.

Example 2

Strengthening of specimens was done up to half of the column height. Allthree specimens were erected with the specifications as shown inTable 1. First course of the bricks was laid in a manner that half brickwas embedded into the 5 inch (0.13 m) thick 1:2:4 reinforced cementconcrete pad as shown in FIG. 4. This reinforced cement concrete pad wasa non-structural element, which was used as a platform over which thecolumns were erected.

TABLE 1 Specimen description No. Description Measurements 1 AverageBrick Size 9″ × 4.5″ × 3″ (0.23 m × 0.11 m × 0.08 m) 2 Cement SandMortar 1:4 3 Cement Ordinary Portland Cement 4 Sand locally available 5Bed Joint Thickness 0.394 in (0.01 m) 6 Curing Time 7 days

Example 3

End of a polyester thread was first tied from one side to the pole. Itwas taken to the other end in fully stretched form, wound around it andbrought back to the tied end. This action completed one cycle and 30similar cycles were completed to obtain the desired width of the stripwhich was 22 mm. The width of the strip was chosen so as to cover theentire width of the mortar joint and some portion of the adjoiningbricks. It was ensured that during this procedure no space remainsbetween two adjacent horizontal runs of the thread. After this, anadhesive was applied on the pre-tensioned thread assembly and allowed todry for 24 hours. When the adhesive dried and threads held on to eachother, small pieces of bonding tape were attached to these strips atgradual intervals to avoid overturning of threads at later stages ofapplication. Ends of the strengthening strips were than sliced by 25 mmon either side to avoid shear splitting of the strands and sealed byapplying heat so as to avoid the loss in pre-tensioning force.Additionally, the cutting ends were bonded and taped more to preventde-bonding along the horizontal runs of thread. The final form of driedstrengthening strip is shown in FIG. 5.

Example 4

Further characterization was performed on the bricks and the strips.Brick test was conducted according to Section 7 and 8 of ASTM C-67 fortheir compressive strength and water absorption. Results are shown inTable 2, and Table 3. Tensile test was conducted on the manufacturedstrengthening strips, and also the commercially available polypropylenebands (pp-band) with the size of 0.6 in×0.02 in (0.015 m×0.0005 m) forcomparison. Results are shown in Table 4, and Table 5. Average tensileload bearing capacity of these newly developed strengthening strips wasmeasured to be approximately 0.70 Ton (6975 N), which was at least threetimes larger than that of the commercially available pp-band which wasmeasured to be about 0.22 Ton (2192 N). Average failure tensile load ofpp-band with same cross-sectional area found by other researchers isreported to be around 0.18 Ton (1794 N), which is compatible with thecurrent findings. [Sathiparan, N., Mayorca, P., Nesheli, K. N.,Guragain, R. and Meguro, K.: “Experimental study on in-plain andout-of-plain behaviour of Masonry Wallettes retrofitted by PP-Bandmeshes”, Seisan Kenkyu, 58 (3): 197-213 (2006); Meguro, K., Mayorca, P.,Sathiparan, N., Guragain, R., and Nesheli, N.: “Shaking Table Tests of ¼Scaled Masonry Models Retrofitted with PP-band Meshes”, Proceedings ofthe Third International Symposium on New Technologies for Urban Safetyof Mega Cities in Asia, Singapore, 1: 9-18, (2005); Navaratnarajah, S.:”Experimental study of PP-band mesh seismic retrofitting for lowearthquake masonry resisting structures: PhD Dissertation, Department ofCivil Engineering, University of Tokyo, Japan, (2008); incorporatedherein by reference in its entirety]

TABLE 2 Compressive strength test on brick units Compressive StrengthTest on Brick Units Sample Dimension of Surface Area Max Load AppliedCompressive strength No. Brick (inches) (inch²) (mm²) (Tons) (KN) (Psi)N/mm² 1 8.9 × 4.4 × 3 39.16 25264 54 538 3039 20.95 2   9 × 4.4 × 3 39.625548 43 428 2393 16.5 3 8.9 × 4.5 × 3 40.05 25839 44 438 2421 16.7 48.9 × 4.4 × 3 39.16 25264 52 518 2927 20.18 5 8.9 × 4.4 × 3 40.05 2583943 428 2340 16.13 Mean 2624 18.09

TABLE 3 Water absorption test on brick units Percentage Absorption teston Brick Units Sample Wet Weight of Sample Dry Weight of Sample % WaterNo. (gm) (gm) Absorption 1 3782 3456 9.4 2 3816 3466 10.0 3 3805 340011.9 4 3792 3462 9.5 5 3808 3458 10.0 Mean 10.2

TABLE 4 Direct tension test on polyester strips Direct Tension Test onStrips Failure Sample Tensile Load Ultimate Stress No. (Tons) (N)(N/mm²) 1 0.70 6975 930 2 0.69 6875 916.6 3 0.71 7074 943.2 Mean 0.706975 930

TABLE 5 Direct tension test on pp-band Direct Tension Test on PP-BandFailure Tensile Sample Load (Tons) Ultimate Stress No. (Tons) (N)(N/mm²) 1 0.22 2192 199.3 2 0.22 2192 199.3 3 0.21 2092 190.2 Mean 0.222192 199.3

Example 5

The strengthening process started by tightly wrapping the polyesterstrips (PS), by hand, at the base joint of the column, as it wasanticipated that the failure initiates at the joints. The wrapping ofthe PS was followed by first wrap of strong bonding tape. It was alsoanticipated that in the absence of any axial loading on top of thecolumn, the failure might be confined at the base of the column.Therefore, one extra PS was provided between the first and the secondbed joint. Afterwards, a global wrap of strong bonding tape was appliedat the base of the column. Vertical PS strips were provided with thesewing action for added confinement. Spacing of the mesh was kept at 4inch×4 inch (0.10 m×0.10 m). Upon completion of the mesh, each bed-jointwas wrapped with two rounds of the binding tape. Cut-off ends of thetape were given on the out-of-plane face to prevent any de-bonding oftape due to in-plane forces. As the final step, a global wrap was usedto protect the column and keep the reinforcement components in place.

Example 6

East-West component of the acceleration time-history of El-Centroearthquake as shown in FIG. 6, was gradually increasing intensitiesusing the single degree of freedom shaking table till the specimensfailed by showing large unstable displacements or toppling over, afterwhich they were observed for failure pattern. Feedback ground motionresponse and displacement response of the specimens were recorded usinga data acquisition system and displacement transducers. The specimen wasattached fixed to the shake table (as shown in FIG. 3) to arrest itsmovement during testing. No vertical axial load was applied on top ofthe column as the aim of this study was to test the specimen under leastfavorable conditions, however it is noted that adding verticalcompressive loading on top the unstrengthened brick masonry columns maypositively increase the strengthening performance as the loading mayreduce sway of the column thereby making the strengthening moreeffective. However, adding the weight of the column might lead to crushthe bricks during the dynamic testing which could affect its crackingpattern. In the reinforced brick masonry column tested here, the basehas a global wrapping and thus crushed bricks at the base confined inplace without having adverse effect on the dynamic performance of thecolumn.

Example 7

Three test specimens were tested in the present study; one controlspecimen (i.e. without any strengthening), and two strengthenedspecimens. Both of the strengthened specimens were applied to the sameground motion acceleration. The following section presents the resultsof strengthened specimen when compared to the control specimen. FIG. 7indicates that the drive ground acceleration given to the specimen andthe feedback ground acceleration had little disparity, which ascertainsthe accuracy of the response as presented below. It is to be mentionedhere that the small disparity in the drive and feedback is owing to thenoise in the electrical signal received by the accelerometer mounted ontop of the actuator; however, the values presented are within theacceptable limits.

FIG. 8 presents the peak ground acceleration (PGA) response of thestrengthened specimen and the unstrengthened control specimen. It can beseen that the strengthened specimen performed much better than thecontrol specimen. It failed at a peak ground acceleration of 2.60m/sec²; which is about 9% higher than the failure peak groundacceleration of control specimen which was 2.40 m/sec². Furthermore itcan be seen from FIG. 8 that the strengthened specimen depicted a muchsmoother response to the ground excitation with periodic sinusoidalmotion up to 30 seconds, whereas the control specimen displays anerratic motion resulting in base cracking failure at around 18 seconds.

Furthermore the displacement response of control and strengthenedspecimen was studied to better evaluate their performance. The intenthere was to investigate the deformational response and the crackingpattern. A detailed literature review was conducted to understand thecrack initiation and propagation mechanism to better understand thecracking response. [Moussa, A., Bell, R. and Tan, L. C.: “Theinteraction of two parallel semi-elliptical surface cracks under tensionand bending”, Journal of Pressure Vessel Technology, 121: 323-326,(1999); Ishida, M., Yoshida, T. and Noguchi, H.: “Parallel array ofsemi-elliptical surface cracks in semi-infinite solid under tension”,Journal of Engineering Fracture Mechanics, 39(5): 845-850, (1991); Shu,M. H., Petit, J. and Bezine, G.: “Stress Intensity factors for severalgroups of equal and parallel cracks in finite plates”, Journal ofEngineering Fracture Mechanics, 49(6): 933-941, (1994); Kamaya, M.: “Acrack growth evaluation method for interacting multiple cracks”, JSMEInternational Journal, 46(1):15-23, (2003); incorporated herein byreference in its entirety] The displacement response of control specimenobtained at failure peak ground acceleration of 2.40 m/sec² was plottedversus time as shown in FIG. 9. It can be observed from the above figurethat the specimen moved as a whole for the first six seconds as the topand bottom end displacements are comparable. Afterwards the specimencracked and reached its maximum displacement of 5 inches between thesixth and seventh second. The shake table was shut down at this pointbecause the column was unconfined and showed ominous signs of toppling.As a result both curves gradually reduce to zero completing the 30second period. The displacement response of strengthened specimen isalso plotted as shown in FIG. 10 having a peak ground failureacceleration of 2.60 m/sec².

FIG. 11A also represents the top and bottom displacement response of thestrengthened specimen prepared using the reading collected fromdisplacement transducers. The purpose of this figure is to present thedisplacement response of the column subject to ground excitation. Fromthe figure, it is clear that the top and bottom end displacements arecomparable for the first two and a half seconds after which the top endbegan to sway largely indicating the initiation of cracking in thejoints of the unstrengthened brick masonry column. It cracked betweenthe sixth and seventh second but still did not topple as its base wasconfined keeping the specimen intact at its position. The specimen wasable to sustain the ground motion for full 30 seconds.

It is interesting to mention the change of mode prior to failure peak asshown in FIG. 11B, which was not observed in the displacement responseof control specimen as shown in FIG. 9. This observation indicates theeffectiveness of confinement in the strengthened specimen. From thefigure it is possible to identify the exact location of the mode change.The mode change indicates that a portion of the applied energy wasabsorbed by the strengthened specimen towards changing the mode.Therefore, the strengthened specimen could sustain larger groundaccelerations compared to the unstrengthened specimen. FIG. 12 shows thedisplacement of the top portion of the strengthened and the controlspecimens at a constant ground acceleration of 2.40 m/sec². Theobjective of this result is to compare the dynamic response ofstrengthened and unstrengthened column at peak ground displacement ofcontrol column so that a clear picture regarding the overall performanceof the unstrengthened brick masonry column can be established. It isobserved that when control specimen was cracked and reached its maximumdisplacement of about 5 inches, the strengthened specimen was stilluncracked and had displaced only about 1 inch as a result of enhancedconfinement provided by the strips and the tapes. Therefore, thestrengthened specimen was better able to endure the deformations whichresulted in smaller displacements at the top leading to a reduced degreeof damage. FIG. 13A represents the top end displacement of controlspecimen, and FIG. 13B represents the top end displacement strengthenedspecimens with respect to their bottom end displacements at thecorresponding failure peak ground acceleration (i.e. 2.40 m/sec² for thecontrol, and 2.60 m/sec² for the strengthened specimen). It is seen thatthe strengthened specimen, FIG. 13B, showed a reduced post crackingdisplacement that the unstrengthened specimen, FIG. 13A, by around 21%implying that the strengthened specimen has an improved dynamicperformance and reduced damage.

Example 8

FIG. 14A and FIG. 14B reveal the post-failure cracks in the controlspecimen. It can be seen that the specimen cracked from the base leadingto a large overturning and shear forces. These forces were induced asthe top end tried to sway greater than the bottom end. First and secondbed-joints underwent total failure with wide cracks of almost 0.3 in(7.6 mm). Both the strengthened specimens were unwrapped prior to crackinspection along the highlighted planes using a blade cutter. Thepurpose of the unwrapping sequence was to inflict as little changes tothe internal geometry as possible so as to obtain an undisturbedanalysis. Care was taken not to cut the strips before observing theircondition and similarly other faces were uncovered to check the cracks.The first strengthened specimen was also cracked from the base but witha noticeable difference in the crack size. In fact, crack size in thestrengthened specimen was significantly narrower than the crack size inthe control specimen. Accordingly, the second strengthened specimen wasunwrapped in a same sequence as explained above. However, afterscrutinizing the cracks of first strengthened specimen one importantchange was made before strengthening the second one. Instead of placingthe polyester strip mesh directly on the bed-joints as in the firstcase, all the horizontal bed-joints were first wrapped tightly by tworounds of binding tape and then the strips were fixed in position.Remaining sequence was unchanged. Since the binding tape sticks morestrongly to its own surface as compared to masonry, this specimen failedat a peak ground acceleration of 2.60 m/sec², as oppose to the firststrengthened specimen that was failed at a peak ground acceleration of2.55 m/sec². This specimen not only failed at the largest peak groundacceleration, but also revealed a better protection from damage at thebase, as shown in FIG. 15A and FIG. 15B. As a result of a slight changein the manufacturing method, base of this specimen sustained greaterground accelerations.

An inexpensive strengthening technique for masonry structures waspresented wherein polyester thread strips were used to reinforce brickmasonry columns. Some dynamic and seismic properties of the unreinforcedand reinforced brick masonry columns were measured and reported using ashake table.

The inexpensive strengthening technique of the present disclosureprovides a reinforced masonry column that has many advantages over theunreinforced column. The technique does not require any skilled laborand it can easily be adopted for strengthening unreinforced brickmasonry columns for under privileged localities using locally availableresources and manpower. The polyester thread strips were shown to beeffective in improving the stiffness and deformational response byproviding confinement to the column. The polyester thread stripsrevealed larger tensile strength compared to commercially availablepolypropylene bands. The polyester thread strips resulted in a uniformstress distribution along the strengthened zone as evident by evenlydistributed cracks, whereas the control specimen failed with one largecrack at the bottom of the column.

The present disclosure provides a practical technique in remoteimpoverished areas by relying on local resources and manpower. A costanalysis revealed that the current method is more economic compared toother existing methods as it employs locally available resources andmanpower, and it does not require skilled labor.

The invention claimed is:
 1. A method of strengthening a brick masonrycolumn comprising bricks and a mortar that holds the bricks together ata plurality of horizontal bed joints, the method comprising: wrappingeach horizontal bed joint in the brick masonry column with at least onelayer of a primary bonding tape; wrapping a polyester threadreinforcement strip on the primary bonding tape at each horizontal bedjoint to form horizontally mounted polyester thread reinforcementstrips; vertically mounting at least one polyester thread reinforcementstrip on each side of the brick masonry column by interweaving throughthe horizontally mounted polyester thread reinforcement strips to form ameshed structure that is wrapped around the brick masonry column;wrapping the horizontally mounted polyester thread reinforcement stripswith at least one layer of a secondary bonding tape; and covering atleast a portion of the brick masonry column, the primary bonding tape,the meshed structure, the secondary bonding tape, or combinationsthereof with at least one layer of a wrapping material.
 2. The method ofclaim 1, wherein a first horizontal bed joint from a bottom of the brickmasonry column is wrapped with at least one layer of the primary bondingtape and at least two layers of the horizontally mounted polyesterthread reinforcement strips.
 3. The method of claim 1, wherein at leasttwo polyester thread reinforcement strips are vertically mounted on eachside of the brick masonry column and the two polyester threadreinforcement strips are separated by a distance of at least 2 cm. 4.The method of claim 1, wherein each mesh of the meshed structure has arectangular shape with a mesh size in the range of 2-30 cm by 2-30 cm.5. The method of claim 1, wherein a width of the horizontally mountedpolyester thread reinforcement strips is in the range of 10-30 mmrelative to horizontal bed joints having a width in the range of 5-15mm, and wherein the horizontally mounted polyester thread reinforcementstrips entirely cover the horizontal bed joints.
 6. The method of claim1, wherein a width of the horizontally mounted polyester threadreinforcement strips is in the range of 10-30 mm relative to the brickmasonry column having a height in the range of 1-10 m.
 7. A method ofmanufacturing polyester thread reinforcement strips, comprising: tying afirst end of a polyester thread to a first pole of a structurecomprising the first pole and a second pole, wherein the first pole andthe second pole are parallel and separated by at least 20 cm; winding asecond end of the polyester thread around the second pole of thestructure and returning the second end of the polyester thread to thefirst pole in stretched form to make a wound cycle, wherein thepolyester thread is perpendicular to the first and the second poles;repeating the winding at least 30 times in a back and forth movement toform a polyester thread assembly, wherein each polyester thread isadjacent and parallel to the polyester thread from a previous woundcycle, and wherein no gap is present between the adjacent and parallelpolyester threads; applying an adhesive to the polyester threadassembly; curing and/or drying the adhesive; and cutting the polyesterthread assembly along the first and the second poles and at least 1 cmfrom each pole to make the polyester thread reinforcement strip.
 8. Themethod of claim 7, wherein the cutting forms cut edges on opposing sidesof the polyester thread reinforcement strip, and the method furthercomprises sealing the cut edges of the polyester thread reinforcementstrip by heating, annealing and/or taping.
 9. The method of claim 7,wherein the polyester thread reinforcement strip has an ultimate tensilestrength at least four times larger and a maximum tensile load bearingcapacity at least three times larger than a substantially similar stripwith polypropylene threads instead of polyester threads.